1. Field of the Invention
The present invention relates to a magnetic head suitable for high density magnetic recording systems such as video tape recorders.
2. Brief Description of the Prior Art
The video tape recorder as a typical high density magnetic recording system has been remarkably improved in recording density to meet size reduction and longer playing needs. Particularly in regard to the head-tape system, efforts for technological innovation have been largely focused on the implementation of shorter wavelengths of recording signals and narrower recording track widths. Particularly, the development of azimuth recording for increasing the track density has contributed considerably to increased recording density, and this technique has been utilized in the great majority of video tape recorder models available today. FIG. 5 is a perspective view showing a typical video head used in azimuth recording and FIG. 6 is a plan view of the head as viewed from the tape sliding surface. For example, a magnetic gap 12 is defined by magnetic cores 11, 11', which may be made of ferrite, for instance, and the plane of the gap is inclined at an angle of .theta. with respect to the plane perpendicular to the direction of head travel (which is parallel to the lateral sides of the head). In the video tape recorder, the recording and reproduction of video signals are performed by a pair of video heads mounted at an interval of 180 degrees on a revolving cylinder. For azimuth recording, the azimuth angles of these two heads are disposed symmetrically with respect to the plane perpendicular to the direction of head travel. Therefore, even when the head scans the adjacent track, the signal in the adjacent track is attenuated by azimuth loss so that substantially no cross-talk is generated. In addition, the width of the guard band between two adjacent tracks can be decreased and in certain cases a high area density can be implemented even without a guard band.
While video tape recorders having a long-playing mode with a slow tape traveling speed have been introduced in recent years to cope with the increasing number of long programs and for the reduction of tape costs, these recorders are generally so designed that the two modes can be used interchangeably to prevent degradation of picture quality on the long-playing mode and for quick interchangeability with the standard mode. To implement both modes in a single video head, the track width of the video head must be selected in such a manner that the picture quality on the standard mode will be preserved as much as possible and, yet, the influence of the immediately adjoining or next adjoining track signal on the long-playing mode will be minimized. Generally, however, the track width has to be larger than the track pitch of the long-playing mode. For example, whereas the pitch for the standard mode is 58 .mu.m and that for the triple play mode is 19.3 .mu.m in the VHS system, a head track width of 30 .mu.m is employed. In recording on such a long-playing mode, the recording track width is narrowed to a given width by overwriting a part of the previously recorded track but the erasure residue of the long-wavelength signal in this overwrite area becomes noise so as to reduce the S/N ratio, thus contributing to the degradation of picture quality on the long-playing mode.